search for: iret

I'm implementing a more efficient version of the Xen iret paravirt_op, so that it can use the real iret instruction where possible. I really need to get access to per-cpu variables, so I can set the event mask state in the vcpu_info structure, but unfortunately at the point where INTERRUPT_RETURN is used in entry.S, the usermode %fs has already been rest...

I'm implementing a more efficient version of the Xen iret paravirt_op, so that it can use the real iret instruction where possible. I really need to get access to per-cpu variables, so I can set the event mask state in the vcpu_info structure, but unfortunately at the point where INTERRUPT_RETURN is used in entry.S, the usermode %fs has already been rest...

i386 Transparent paravirtualization patch #1. Add support for interrupt holdoff to the entry.S fault and syscall paths. This is a straightforward macro-ization for the default sub-architecture. Note that CLI, STI and IRET may be called with non-flat segments because guest %ds and %es segments are live at the time. Any alternative implementation (such as a virtual interrupt mask) is required to be compatible with this requirement. This makes maintenance of the code in entry.S much more easy, and eliminates some very...

i386 Transparent paravirtualization patch #1. Add support for interrupt holdoff to the entry.S fault and syscall paths. This is a straightforward macro-ization for the default sub-architecture. Note that CLI, STI and IRET may be called with non-flat segments because guest %ds and %es segments are live at the time. Any alternative implementation (such as a virtual interrupt mask) is required to be compatible with this requirement. This makes maintenance of the code in entry.S much more easy, and eliminates some very...

On Fri, Aug 07, 2020 at 10:38:23AM +0200, Juergen Gross wrote: > -# else > - const unsigned char cpu_iret[1]; > -# endif > }; > > static const struct patch_xxl patch_data_xxl = { > @@ -42,7 +38,6 @@ static const struct patch_xxl patch_data_xxl = { > .irq_save_fl = { 0x9c, 0x58 }, // pushf; pop %[re]ax > .mmu_read_cr2 = { 0x0f, 0x20, 0xd0 }, // mov %cr2, %[re]ax > .mm...

On Fri, Aug 07, 2020 at 10:38:23AM +0200, Juergen Gross wrote: > -# else > - const unsigned char cpu_iret[1]; > -# endif > }; > > static const struct patch_xxl patch_data_xxl = { > @@ -42,7 +38,6 @@ static const struct patch_xxl patch_data_xxl = { > .irq_save_fl = { 0x9c, 0x58 }, // pushf; pop %[re]ax > .mmu_read_cr2 = { 0x0f, 0x20, 0xd0 }, // mov %cr2, %[re]ax > .mm...

...t iV4LbufferSize; unsigned char* pucV4Lbuffer; struct video_mmap tV4LvideoMMap; int V4L_Init( const char *szDevice ) { struct video_capability tVideoCapability; struct video_channel tVideoChannel; struct video_mbuf tVideoMBuf; int iRet = 0; printf( "+++ V4L_Init() \n" ); if( szDevice == NULL ) { fprintf( stderr, "### Invalid device name \n" ); iRet = -1; goto V4L_Init_quit; } if( ( iV4Lfd = open( szDevice, O_RDWR ) ) == -1 ) { perror( "### open()&qu...

The self_nmi() code cause''s an NMI to be triggered by sending an APIC message to the local processor. However, NMIs are blocked by the VMEXIT, until the next iret or VMENTER. Volume 3 Chapter 27 Section 1 of the Intel SDM states: An NMI causes subsequent NMIs to be blocked, but only after the VM exit completes. As a result, as soon as the VMENTER happens, an immediate VMEXIT happens as a result of the queued NMI. We have seen hundreds of iterations of th...

xen: use iret directly where possible Most of the time we can simply use the iret instruction to exit the kernel, rather than having to use the iret hypercall - the only exception is if we're returning into vm86 mode, or from delivering an NMI (which we don't support yet). When running native, iret has...

xen: use iret directly where possible Most of the time we can simply use the iret instruction to exit the kernel, rather than having to use the iret hypercall - the only exception is if we're returning into vm86 mode, or from delivering an NMI (which we don't support yet). When running native, iret has...

xen: use iret directly where possible Most of the time we can simply use the iret instruction to exit the kernel, rather than having to use the iret hypercall - the only exception is if we're returning into vm86 mode, or from delivering an NMI (which we don't support yet). When running native, iret has...

[ Expand, correct and clarify comments; minor code change. ] Most of the time we can simply use the iret instruction to exit the kernel, rather than having to use the iret hypercall - the only exception is if we're returning into vm86 mode, or from delivering an NMI (which we don't support yet). When running native, iret has the behaviour of testing for a pending interrupt atomically with re-...

[ Expand, correct and clarify comments; minor code change. ] Most of the time we can simply use the iret instruction to exit the kernel, rather than having to use the iret hypercall - the only exception is if we're returning into vm86 mode, or from delivering an NMI (which we don't support yet). When running native, iret has the behaviour of testing for a pending interrupt atomically with re-...

...the native processor exception frame interface. N.B. Sti; Sysexit is a required abstraction, as the STI instruction implies holdoff of interrupts, which is destroyed by any NOP padding. There is a race condition is present in all virtualization solutions in which the guest kernel may issue a raw IRET instruction, as the IRET instruction is not properly virtualizable on non-hardware assisted Intel platforms. This is because the interrupt flag, which indicates whether an IRQ may be delivered, is not changed by the instruction when running without I/O privilege level Thus, there is no way to ato...

...the native processor exception frame interface. N.B. Sti; Sysexit is a required abstraction, as the STI instruction implies holdoff of interrupts, which is destroyed by any NOP padding. There is a race condition is present in all virtualization solutions in which the guest kernel may issue a raw IRET instruction, as the IRET instruction is not properly virtualizable on non-hardware assisted Intel platforms. This is because the interrupt flag, which indicates whether an IRQ may be delivered, is not changed by the instruction when running without I/O privilege level Thus, there is no way to ato...

...@@ sysenter_past_esp: * Return back to the vDSO, which will pop ecx and edx. * Don't bother with DS and ES (they already contain __USER_DS). */ - ENABLE_INTERRUPTS_SYSEXIT + sti + sysexit .pushsection .fixup, "ax" 2: movl $0, PT_FS(%esp) @@ -554,11 +555,6 @@ ENTRY(native_iret) iret _ASM_EXTABLE(native_iret, iret_exc) END(native_iret) - -ENTRY(native_irq_enable_sysexit) - sti - sysexit -END(native_irq_enable_sysexit) #endif ENTRY(overflow) --- a/arch/x86/include/asm/paravirt.h +++ b/arch/x86/include/asm/paravirt.h @@ -938,13 +938,6 @@ extern void default_banner(...

...@@ sysenter_past_esp: * Return back to the vDSO, which will pop ecx and edx. * Don't bother with DS and ES (they already contain __USER_DS). */ - ENABLE_INTERRUPTS_SYSEXIT + sti + sysexit .pushsection .fixup, "ax" 2: movl $0, PT_FS(%esp) @@ -552,11 +553,6 @@ ENTRY(native_iret) iret _ASM_EXTABLE(native_iret, iret_exc) END(native_iret) - -ENTRY(native_irq_enable_sysexit) - sti - sysexit -END(native_irq_enable_sysexit) #endif ENTRY(overflow) diff --git a/arch/x86/include/asm/paravirt.h b/arch/x86/include/asm/paravirt.h index 10d0596..c28518e 100644 --- a/arch/x86/...

The first patch fixes Xen PV regression introduced by 32-bit rewrite. Unlike the earlier version it uses ALTERNATIVE instruction and avoids using xen_sysexit (and sysret32 in compat mode) pv ops, as suggested by Andy. (I ended up patching TEST with XOR to avoid extra NOPs, even though I said yesterday it would be wrong. It's not wrong) As result of this patch irq_enable_sysexit and

The first patch fixes Xen PV regression introduced by 32-bit rewrite. Unlike the earlier version it uses ALTERNATIVE instruction and avoids using xen_sysexit (and sysret32 in compat mode) pv ops, as suggested by Andy. (I ended up patching TEST with XOR to avoid extra NOPs, even though I said yesterday it would be wrong. It's not wrong) As result of this patch irq_enable_sysexit and

...@@ sysenter_past_esp: * Return back to the vDSO, which will pop ecx and edx. * Don't bother with DS and ES (they already contain __USER_DS). */ - ENABLE_INTERRUPTS_SYSEXIT + sti + sysexit .pushsection .fixup, "ax" 2: movl $0, PT_FS(%esp) @@ -554,11 +555,6 @@ ENTRY(native_iret) iret _ASM_EXTABLE(native_iret, iret_exc) END(native_iret) - -ENTRY(native_irq_enable_sysexit) - sti - sysexit -END(native_irq_enable_sysexit) #endif ENTRY(overflow) --- a/arch/x86/include/asm/paravirt.h +++ b/arch/x86/include/asm/paravirt.h @@ -938,13 +938,6 @@ extern void default_banner(...