From: "Jörg Rödel" <joro@8bytes.org>
To: Borislav Petkov <bp@alien8.de>
Cc: Peter Zijlstra <peterz@infradead.org>,
x86@kernel.org, Joan Bruguera <joanbrugueram@gmail.com>,
linux-kernel@vger.kernel.org, Juergen Gross <jgross@suse.com>,
"Rafael J. Wysocki" <rafael@kernel.org>,
xen-devel <xen-devel@lists.xenproject.org>,
Jan Beulich <jbeulich@suse.com>,
Roger Pau Monne <roger.pau@citrix.com>,
Kees Cook <keescook@chromium.org>,
mark.rutland@arm.com, Andrew Cooper <Andrew.Cooper3@citrix.com>,
"H. Peter Anvin" <hpa@zytor.com>
Subject: Re: [PATCH v2 2/7] x86/boot: Delay sev_verify_cbit() a bit
Date: Fri, 20 Jan 2023 13:43:50 +0100 [thread overview]
Message-ID: <Y8qMhhEOA6MuGMxm@8bytes.org> (raw)
In-Reply-To: <Y8lDN73cNOmNuciV@zn.tnic>
On Thu, Jan 19, 2023 at 02:18:47PM +0100, Borislav Petkov wrote:
> So, can we do that C-bit verification once on the BSP, *in C* which would be a
> lot easier, and be done with it?
>
> Once it is verified there, the bit is the same on all APs so all good.
Yes, I think this is safe to do. The page-table the APs will use to boot
already has the correct C-bit set, and the position is verified on the
BSP. Further, the C-bit position is a hardware capability and there is
no chance the APs will have it at a different position than the BSP.
Even if the HV is lying to the VM by faking CPUID on the APs it wouldn't
matter, because the position is not read again on the APs.
Regards,
Joerg
next prev parent reply other threads:[~2023-01-20 12:43 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-01-16 14:25 [PATCH v2 0/7] x86: retbleed=stuff fixes Peter Zijlstra
2023-01-16 14:25 ` [PATCH v2 1/7] x86/boot: Remove verify_cpu() from secondary_startup_64() Peter Zijlstra
2023-01-17 9:25 ` Ingo Molnar
2023-01-18 9:45 ` Peter Zijlstra
2023-01-18 11:46 ` kirill.shutemov
2023-01-19 19:35 ` H. Peter Anvin
2023-01-26 14:15 ` Peter Zijlstra
2023-01-16 14:25 ` [PATCH v2 2/7] x86/boot: Delay sev_verify_cbit() a bit Peter Zijlstra
2023-01-19 13:18 ` Borislav Petkov
2023-01-20 12:43 ` Jörg Rödel [this message]
2023-01-16 14:25 ` [PATCH v2 3/7] x86/power: De-paravirt restore_processor_state() Peter Zijlstra
2023-01-20 20:26 ` Borislav Petkov
2023-01-16 14:25 ` [PATCH v2 4/7] x86/power: Inline write_cr[04]() Peter Zijlstra
2023-01-20 20:29 ` Borislav Petkov
2023-01-16 14:25 ` [PATCH v2 5/7] x86/callthunk: No callthunk for restore_processor_state() Peter Zijlstra
2023-01-16 14:25 ` [PATCH v2 6/7] x86/power: Sprinkle some noinstr Peter Zijlstra
2023-01-17 9:31 ` Ingo Molnar
2023-01-17 11:29 ` Peter Zijlstra
2023-01-17 11:54 ` Ingo Molnar
2023-01-16 14:25 ` [PATCH v2 7/7] PM / hibernate: Add minimal noinstr annotations Peter Zijlstra
2023-01-18 1:54 ` [PATCH v2 0/7] x86: retbleed=stuff fixes Joan Bruguera
2023-05-16 13:59 ` Josh Poimboeuf
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