From: Borislav Petkov <bp@alien8.de>
To: Joerg Roedel <joro@8bytes.org>
Cc: x86@kernel.org, Joerg Roedel <jroedel@suse.de>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
Dave Hansen <dave.hansen@linux.intel.com>,
Andy Lutomirski <luto@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Kees Cook <keescook@chromium.org>,
Arvind Sankar <nivedita@alum.mit.edu>,
Martin Radev <martin.b.radev@gmail.com>,
Tom Lendacky <thomas.lendacky@amd.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3 1/5] x86/boot/compressed/64: Introduce sev_status
Date: Mon, 26 Oct 2020 19:27:06 +0100 [thread overview]
Message-ID: <20201026182706.GG22116@zn.tnic> (raw)
In-Reply-To: <20201021123938.3696-2-joro@8bytes.org>
On Wed, Oct 21, 2020 at 02:39:34PM +0200, Joerg Roedel wrote:
> From: Joerg Roedel <jroedel@suse.de>
>
> Introduce sev_status and initialize it together with sme_me_mask to have
> an indicator which SEV features are enabled.
>
> Signed-off-by: Joerg Roedel <jroedel@suse.de>
> ---
> arch/x86/boot/compressed/mem_encrypt.S | 10 +++++++++-
> 1 file changed, 9 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/boot/compressed/mem_encrypt.S b/arch/x86/boot/compressed/mem_encrypt.S
> index dd07e7b41b11..2192b3bd78d8 100644
> --- a/arch/x86/boot/compressed/mem_encrypt.S
> +++ b/arch/x86/boot/compressed/mem_encrypt.S
> @@ -81,6 +81,13 @@ SYM_FUNC_START(set_sev_encryption_mask)
>
> bts %rax, sme_me_mask(%rip) /* Create the encryption mask */
>
> + /* Read sev_status */
> + movl $MSR_AMD64_SEV, %ecx
> + rdmsr
> + shlq $32, %rdx
> + orq %rdx, %rax
> + movq %rax, sev_status(%rip)
A couple of lines above you call get_sev_encryption_bit() which already
reads MSR_AMD64_SEV. Why not set sev_status there too instead of reading
that MSR again here?
It can read that MSR once and use sev_status(%rip) from then on to avoid
reading that MSR multiple times...
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
next prev parent reply other threads:[~2020-10-26 18:27 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-21 12:39 [PATCH v3 0/5] x86/sev-es: Mitigate some HV attack vectors Joerg Roedel
2020-10-21 12:39 ` [PATCH v3 1/5] x86/boot/compressed/64: Introduce sev_status Joerg Roedel
2020-10-26 18:27 ` Borislav Petkov [this message]
2020-10-28 8:23 ` Joerg Roedel
2020-10-28 16:50 ` Arvind Sankar
2020-10-28 16:55 ` Joerg Roedel
2020-10-21 12:39 ` [PATCH v3 2/5] x86/boot/compressed/64: Add CPUID sanity check to early #VC handler Joerg Roedel
2020-10-27 10:38 ` Borislav Petkov
2020-10-28 8:31 ` Joerg Roedel
2020-10-21 12:39 ` [PATCH v3 3/5] x86/boot/compressed/64: Check SEV encryption in 64-bit boot-path Joerg Roedel
2020-10-27 11:08 ` Borislav Petkov
2020-10-28 8:38 ` Joerg Roedel
2020-10-27 11:09 ` Borislav Petkov
2020-10-21 12:39 ` [PATCH v3 4/5] x86/head/64: Check SEV encryption before switching to kernel page-table Joerg Roedel
2020-10-27 11:20 ` Borislav Petkov
2020-10-21 12:39 ` [PATCH v3 5/5] x86/sev-es: Do not support MMIO to/from encrypted memory Joerg Roedel
2020-10-27 11:26 ` Borislav Petkov
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