From: Paolo Bonzini <pbonzini@redhat.com>
To: stsp <stsp2@yandex.ru>, Maxim Levitsky <mlevitsk@redhat.com>
Cc: Sean Christopherson <seanjc@google.com>,
Vitaly Kuznetsov <vkuznets@redhat.com>,
Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
Jan Kiszka <jan.kiszka@siemens.com>,
x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
kvm@vger.kernel.org
Subject: Re: [PATCH v2] KVM: X86: Fix exception untrigger on ret to user
Date: Wed, 7 Jul 2021 01:45:52 +0200 [thread overview]
Message-ID: <b1976445-1b88-8a6c-24ee-8a3844db3885@redhat.com> (raw)
In-Reply-To: <dc6a64d0-a77e-b85e-6a8e-c5ca3b42dd59@yandex.ru>
On 07/07/21 01:06, stsp wrote:
> What I ask is how SHOULD the
> KVM_SET_REGS and KVM_SET_SREGS
> behave when someone (mistakenly)
> calls them with the exception pending.
> Should they return an error
> instead of canceling exception?
In theory, KVM_SET_REGS and KVM_SET_SREGS should do nothing but set the
value of the registers. They not should clear either
vcpu->arch.exception.pending or vcpu->arch.exception.injected. I'm wary
of changing that and breaking users of KVM, though.
In this case the problem is that, with a pending exception, you should
not inject the interrupt (doesn't matter if it's with KVM_SET_REGS or
KVM_INTERRUPT). Raising a page fault is part of executing the previous
instruction, and interrupts are only recognized at instruction
boundaries. Therefore, you need to test ready_for_interrupt_injection,
and possibly use request_interrupt_window, before calling KVM_SET_REGS.
The patch you identified as the culprit does have a bug, but that's
fixed in kvm_cpu_accept_dm_intr as I suggested in the other thread.
Paolo
next prev parent reply other threads:[~2021-07-06 23:46 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-28 12:48 [PATCH v2] KVM: X86: Fix exception untrigger on ret to user Stas Sergeev
2021-06-28 14:29 ` Maxim Levitsky
2021-06-28 15:09 ` stsp
2021-06-28 16:50 ` Jim Mattson
2021-06-28 17:00 ` stsp
2021-07-06 11:49 ` Maxim Levitsky
2021-07-06 12:06 ` stsp
2021-07-06 20:29 ` Maxim Levitsky
2021-07-06 21:50 ` stsp
2021-07-06 23:00 ` Maxim Levitsky
2021-07-06 23:06 ` stsp
2021-07-06 23:45 ` Paolo Bonzini [this message]
2021-07-06 23:51 ` stsp
2021-07-07 0:13 ` Paolo Bonzini
2021-07-07 16:16 ` Jim Mattson
2021-07-07 16:34 ` stsp
2021-07-07 16:46 ` Jim Mattson
2021-07-07 16:58 ` stsp
2021-07-07 17:39 ` Jim Mattson
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