Borislav Petkov
2020-May-20 09:14 UTC
[PATCH v3 40/75] x86/sev-es: Compile early handler code into kernel image
On Tue, Apr 28, 2020 at 05:16:50PM +0200, Joerg Roedel wrote:> +static inline u64 sev_es_rd_ghcb_msr(void) > +{ > + return native_read_msr(MSR_AMD64_SEV_ES_GHCB); > +} > + > +static inline void sev_es_wr_ghcb_msr(u64 val) > +{ > + u32 low, high; > + > + low = (u32)(val); > + high = (u32)(val >> 32); > + > + native_write_msr(MSR_AMD64_SEV_ES_GHCB, low, high); > +}Instead of duplicating those two, you can lift the ones in the compressed image into sev-es.h and use them here. I don't care one bit about the MSR tracepoints in native_*_msr().> +static enum es_result vc_write_mem(struct es_em_ctxt *ctxt, > + char *dst, char *buf, size_t size) > +{ > + unsigned long error_code = X86_PF_PROT | X86_PF_WRITE; > + char __user *target = (char __user *)dst; > + u64 d8; > + u32 d4; > + u16 d2; > + u8 d1; > + > + switch (size) { > + case 1: > + memcpy(&d1, buf, 1); > + if (put_user(d1, target)) > + goto fault; > + break; > + case 2: > + memcpy(&d2, buf, 2); > + if (put_user(d2, target)) > + goto fault; > + break; > + case 4: > + memcpy(&d4, buf, 4); > + if (put_user(d4, target)) > + goto fault; > + break; > + case 8: > + memcpy(&d8, buf, 8); > + if (put_user(d8, target)) > + goto fault;Ok, those (and below) memcpys get nicely optimized to MOVs by the compiler here. -- Regards/Gruss, Boris. https://people.kernel.org/tglx/notes-about-netiquette
Joerg Roedel
2020-Jun-04 11:54 UTC
[PATCH v3 40/75] x86/sev-es: Compile early handler code into kernel image
On Wed, May 20, 2020 at 11:14:15AM +0200, Borislav Petkov wrote:> On Tue, Apr 28, 2020 at 05:16:50PM +0200, Joerg Roedel wrote: > > +static inline u64 sev_es_rd_ghcb_msr(void) > > +{ > > + return native_read_msr(MSR_AMD64_SEV_ES_GHCB); > > +} > > + > > +static inline void sev_es_wr_ghcb_msr(u64 val) > > +{ > > + u32 low, high; > > + > > + low = (u32)(val); > > + high = (u32)(val >> 32); > > + > > + native_write_msr(MSR_AMD64_SEV_ES_GHCB, low, high); > > +} > > Instead of duplicating those two, you can lift the ones in the > compressed image into sev-es.h and use them here. I don't care one bit > about the MSR tracepoints in native_*_msr().It is not only the trace-point, this would also eliminate exception handling in case the MSR access triggers a #GP. The "Unhandled MSR read/write" messages would turn into a "General Protection Fault" message. Joerg
Borislav Petkov
2020-Jun-04 15:19 UTC
[PATCH v3 40/75] x86/sev-es: Compile early handler code into kernel image
On Thu, Jun 04, 2020 at 01:54:13PM +0200, Joerg Roedel wrote:> It is not only the trace-point, this would also eliminate exception > handling in case the MSR access triggers a #GP. The "Unhandled MSR > read/write" messages would turn into a "General Protection Fault" > message.But the early ones can trigger a #GP too. And there we can't handle those #GPs. Why would the late ones need exception handling all of a sudden? And for the GHCB MSR, of all MSRs which the SEV-ES guest has used so far to bootstrap?! -- Regards/Gruss, Boris. https://people.kernel.org/tglx/notes-about-netiquette
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- [PATCH v3 40/75] x86/sev-es: Compile early handler code into kernel image
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