lkml.org 
[lkml]   [2024]   [Apr]   [18]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
SubjectRe: [PATCH v4 1/5] x86/kexec: do unconditional WBINVD for bare-metal in stop_this_cpu()
From
On 4/18/24 06:48, Kai Huang wrote:
>

..

> Signed-off-by: Kai Huang <kai.huang@intel.com>
> Suggested-by: Borislav Petkov <bp@alien8.de>
> Cc: Tom Lendacky <thomas.lendacky@amd.com>
> Cc: Dave Young <dyoung@redhat.com>

Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>

> ---
>
> v3 -> v4:
> - Update part of changelog based on Kirill's version (with minor tweak).
> - Use "exception (#VE or #VC)" for TDX and SEV-ES/SEV-SNP in changelog
> and comments. (Kirill, Tom)
> - Point out "WBINVD is not necessary for TDX and SEV-ES/SEV-SNP guests"
> in the comment. (Tom)
>
> v2 -> v3:
> - Change to only do WBINVD for bare metal
>
> ---
> arch/x86/kernel/process.c | 19 +++++++++----------
> 1 file changed, 9 insertions(+), 10 deletions(-)
>
> diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
> index b8441147eb5e..d3c904bfe874 100644
> --- a/arch/x86/kernel/process.c
> +++ b/arch/x86/kernel/process.c
> @@ -813,18 +813,17 @@ void __noreturn stop_this_cpu(void *dummy)
> mcheck_cpu_clear(c);
>
> /*
> - * Use wbinvd on processors that support SME. This provides support
> - * for performing a successful kexec when going from SME inactive
> - * to SME active (or vice-versa). The cache must be cleared so that
> - * if there are entries with the same physical address, both with and
> - * without the encryption bit, they don't race each other when flushed
> - * and potentially end up with the wrong entry being committed to
> - * memory.
> + * The kernel could leave caches in incoherent state on SME/TDX
> + * capable platforms. Flush cache to avoid silent memory
> + * corruption for these platforms.
> *
> - * Test the CPUID bit directly because the machine might've cleared
> - * X86_FEATURE_SME due to cmdline options.
> + * stop_this_cpu() isn't a fast path, just do WBINVD for bare-metal
> + * to cover both SME and TDX. It isn't necessary to perform WBINVD
> + * in a guest and performing one could result in an exception (#VE
> + * or #VC) for a TDX or SEV-ES/SEV-SNP guest that the guest may
> + * not be able to handle (e.g., TDX guest panics if it sees #VE).
> */
> - if (c->extended_cpuid_level >= 0x8000001f && (cpuid_eax(0x8000001f) & BIT(0)))
> + if (!boot_cpu_has(X86_FEATURE_HYPERVISOR))
> native_wbinvd();
>
> /*

\
 
 \ /
  Last update: 2024-05-27 16:45    [W:0.359 / U:1.488 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site