similar to: [RFC PATCH 0/3] x86/paravirt: Get rid of paravirt patching

All functions referenced via __PV_IS_CALLEE_SAVE() need to be assembler functions, as those functions calls are hidden from gcc. In case the kernel is compiled with "-fzero-call-used-regs" the compiler will clobber caller-saved registers at the end of C functions, which will result in unexpectedly zeroed registers at the call site of the related paravirt functions. Replace the C

All functions referenced via __PV_IS_CALLEE_SAVE() need to be assembler functions, as those functions calls are hidden from gcc. In case the kernel is compiled with "-fzero-call-used-regs" the compiler will clobber caller-saved registers at the end of C functions, which will result in unexpectedly zeroed registers at the call site of the related paravirt functions. Replace the C

Any comments? On 08.06.23 16:03, Juergen Gross wrote: > This is a small series getting rid of paravirt patching by switching > completely to alternative patching for the same functionality. > > The basic idea is to add the capability to switch from indirect to > direct calls via a special alternative patching option. > > This removes _some_ of the paravirt macro maze, but

This changes the pv ops code generation to more closely match reality. For example, instead of: callq *0xffffffff81e3a400 (pv_irq_ops.save_fl) vmlinux will now show: pushfq pop %rax nop nop nop nop nop which is what the runtime version of the code will show in most cases. This idea was suggested by Andy Lutomirski. The benefits are: - For the most common runtime cases

This changes the pv ops code generation to more closely match reality. For example, instead of: callq *0xffffffff81e3a400 (pv_irq_ops.save_fl) vmlinux will now show: pushfq pop %rax nop nop nop nop nop which is what the runtime version of the code will show in most cases. This idea was suggested by Andy Lutomirski. The benefits are: - For the most common runtime cases

This series reverts the in-kernel workarounds for inlining issues. The commit description of 77b0bf55bc67 mentioned "We also hope that GCC will eventually get fixed,..." Now, GCC provides a solution. https://gcc.gnu.org/onlinedocs/gcc/Extended-Asm.html explains the new "asm inline" syntax. The performance issue will be eventually solved. [About Code cleanups] I know Nadam

This series reverts the in-kernel workarounds for inlining issues. The commit description of 77b0bf55bc67 mentioned "We also hope that GCC will eventually get fixed,..." Now, GCC provides a solution. https://gcc.gnu.org/onlinedocs/gcc/Extended-Asm.html explains the new "asm inline" syntax. The performance issue will be eventually solved. [About Code cleanups] I know Nadam

With CONFIG_PARAVIRT, the kernel .text is littered with a bunch of calls to pv_irq_ops function pointers, like: callq *0xffffffff81e3a400 (pv_irq_ops.save_fl) In non-Xen paravirt environments -- including native, KVM, Hyper-V, and VMware -- the above code gets patched by native_patch() to look like this instead: pushfq pop %rax nopl 0x0(%rax,%rax,1) So in most scenarios,

Hi Andi, Here's a little batch of cleanups: - re-enable VDSO when PARAVIRT is enabled - make the parainstructions symbols match the other altinstructions naming convention - add kernel command-line options to disable altinstructions for smp and pv_ops Oh, and I'm mailing your noreplacement patch back at you, for no particularly good reason. J --

Hi Andi, Here's a little batch of cleanups: - re-enable VDSO when PARAVIRT is enabled - make the parainstructions symbols match the other altinstructions naming convention - add kernel command-line options to disable altinstructions for smp and pv_ops Oh, and I'm mailing your noreplacement patch back at you, for no particularly good reason. J --

Hi Andi, Here's a repost of the paravirt_ops update series I posted the other day. Since then, I found a few potential bugs with patching clobbering, cleaned up and documented paravirt.h and the patching machinery. Overview: add-MAINTAINERS.patch obvious remove-CONFIG_DEBUG_PARAVIRT.patch No longer meaningful or needed. paravirt-nop.patch Clean up nop paravirt_ops functions, mainly to

Hi Andi, Here's a repost of the paravirt_ops update series I posted the other day. Since then, I found a few potential bugs with patching clobbering, cleaned up and documented paravirt.h and the patching machinery. Overview: add-MAINTAINERS.patch obvious remove-CONFIG_DEBUG_PARAVIRT.patch No longer meaningful or needed. paravirt-nop.patch Clean up nop paravirt_ops functions, mainly to

Is it OK for section .parainstructions to reference exit.text? I'm seeing: WARNING: drivers/net/hamradio/scc.o - Section mismatch: reference to .exit.text: from .parainstructions after '' (at offset 0x0) WARNING: drivers/net/hamradio/scc.o - Section mismatch: reference to .exit.text: from .parainstructions after '' (at offset 0x8) If that's OK, we need a small patch to

Is it OK for section .parainstructions to reference exit.text? I'm seeing: WARNING: drivers/net/hamradio/scc.o - Section mismatch: reference to .exit.text: from .parainstructions after '' (at offset 0x0) WARNING: drivers/net/hamradio/scc.o - Section mismatch: reference to .exit.text: from .parainstructions after '' (at offset 0x8) If that's OK, we need a small patch to

On Wed, Jul 15, 2020 at 11:13:37AM +0200, Joerg Roedel wrote: > On Wed, Jul 15, 2020 at 10:47:52AM +0200, Peter Zijlstra wrote: > > On Tue, Jul 14, 2020 at 02:09:05PM +0200, Joerg Roedel wrote: > > > > > @@ -1028,6 +1036,16 @@ DEFINE_IDTENTRY_VC_SAFE_STACK(exc_vmm_communication) > > > struct ghcb *ghcb; > > > > > >

On Wed, Jul 15, 2020 at 11:13:37AM +0200, Joerg Roedel wrote: > On Wed, Jul 15, 2020 at 10:47:52AM +0200, Peter Zijlstra wrote: > > On Tue, Jul 14, 2020 at 02:09:05PM +0200, Joerg Roedel wrote: > > > > > @@ -1028,6 +1036,16 @@ DEFINE_IDTENTRY_VC_SAFE_STACK(exc_vmm_communication) > > > struct ghcb *ghcb; > > > > > >

The long term plan has been to replace Xen PV guests by PVH. The first victim of that plan are now 32-bit PV guests, as those are used only rather seldom these days. Xen on x86 requires 64-bit support and with Grub2 now supporting PVH officially since version 2.04 there is no need to keep 32-bit PV guest support alive in the Linux kernel. Additionally Meltdown mitigation is not available in the

The long term plan has been to replace Xen PV guests by PVH. The first victim of that plan are now 32-bit PV guests, as those are used only rather seldom these days. Xen on x86 requires 64-bit support and with Grub2 now supporting PVH officially since version 2.04 there is no need to keep 32-bit PV guest support alive in the Linux kernel. Additionally Meltdown mitigation is not available in the

The long term plan has been to replace Xen PV guests by PVH. The first victim of that plan are now 32-bit PV guests, as those are used only rather seldom these days. Xen on x86 requires 64-bit support and with Grub2 now supporting PVH officially since version 2.04 there is no need to keep 32-bit PV guest support alive in the Linux kernel. Additionally Meltdown mitigation is not available in the

Hi Andi, This series of patches updates paravirt_ops in various ways. Some of the changes are plain cleanups and improvements, and some add some interfaces necessary for Xen. The brief overview: add-MAINTAINERS.patch - obvious remove-CONFIG_DEBUG_PARAVIRT.patch - no longer needed paravirt-nop.patch - mark nop operations consistently paravirt-pte-accessors.patch - operations to pack/unpack