linux-kernel - [PATCH 0/2] KVM: xen: update shared_info when long

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Message-Id: <20231201104536.947-1-paul@xen.org>
Date:   Fri,  1 Dec 2023 10:45:34 +0000
From:   Paul Durrant <paul@....org>
To:     David Woodhouse <dwmw2@...radead.org>, Paul Durrant <paul@....org>,
        Sean Christopherson <seanjc@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH 0/2] KVM: xen: update shared_info when long_mode is set

From: Paul Durrant <pdurrant@...zon.com>

This series is based on my v9 of my "update shared_info and vcpu_info
handling" series [1] and fixes an issue that was latent before the
"allow shared_info to be mapped by fixed HVA" patch of that series allowed
a VMM to set up shared_info before the VM booted and then leave it alone.

The problem was noticed when the guest wallclock apparently reverted to
the Unix epoch. This was because, when the shared_info was set up the
guest's long_mode flag was unset and hence the wallclock was intialized
in the place where a 32-bit guest would expect to find it. The 64-bit
guest being tested instead found zero-ed out memory.

Fix the the issue by first separating the initialization of the
shared_info content from setting its location (by HVA or GPA) and then
(re-)initializing the content any time the long_mode flag is changed.

[1] https://lore.kernel.org/kvm/20231122121822.1042-1-paul@xen.org/

Paul Durrant (2):
  KVM: xen: separate initialization of shared_info cache and content
  KVM: xen: (re-)initialize shared_info if guest (32/64-bit) mode is set

 arch/x86/kvm/xen.c | 84 ++++++++++++++++++++++++++++------------------
 1 file changed, 52 insertions(+), 32 deletions(-)

base-commit: 369e9826edfd346f259471e521c03e12bb0ab476
-- 
2.39.2