Messages in this thread Patch in this message | | | Subject | Re: [RFC v2-fix-v4 1/1] x86/tdx: Skip WBINVD instruction for TDX guest | From | "Kuppuswamy, Sathyanarayanan" <> | Date | Wed, 9 Jun 2021 11:24:39 -0700 |
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On 6/9/21 10:31 AM, Dan Williams wrote: >> If you want to apply this fix for all hypervisors (using boot_cpu_has >> (X86_FEATURE_HYPERVISOR) check), then we don't need any TDX specific >> reference in commit log right? It can be generalized for all VM guests. >> >> agree? > No, because there is a note needed about the integrity implications in > the TDX case that makes it distinct from typical hypervisor enabling.
Generalized the commit log (but left the TDX related info). Final version will look like below.
x86: Skip WBINVD instruction for VM guest
VM guests that supports ACPI, use standard ACPI mechanisms to signal sleep state entry (including reboot) to the host. The ACPI specification mandates WBINVD on any sleep state entry with the expectation that the platform is only responsible for maintaining the state of memory over sleep states, not preserving dirty data in any CPU caches. ACPI cache flushing requirements pre-date the advent of virtualization. Given guest sleep state entry does not affect any host power rails it is not required to flush caches. The host is responsible for maintaining cache state over its own bare metal sleep state transitions that power-off the cache. A TDX guest, unlike a typical guest, will machine check if the CPU cache is powered off.
--- a/arch/x86/include/asm/acenv.h +++ b/arch/x86/include/asm/acenv.h @@ -10,10 +10,15 @@ #define _ASM_X86_ACENV_H
#include <asm/special_insns.h> +#include <asm/cpu.h>
/* Asm macros */
-#define ACPI_FLUSH_CPU_CACHE() wbinvd() +#define ACPI_FLUSH_CPU_CACHE() \ +do { \ + if (!boot_cpu_has(X86_FEATURE_HYPERVISOR)) \ + wbinvd(); \ +} while (0)
int __acpi_acquire_global_lock(unsigned int *lock); int __acpi_release_global_lock(unsigned int *lock); -- Sathyanarayanan Kuppuswamy Linux Kernel Developer
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