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Message-ID: <207d6598c8b74161efc38bd18b476ca8626786b1.camel@redhat.com>
Date: Tue, 02 Apr 2024 10:05:24 -0400
From: Maxim Levitsky <mlevitsk@...hat.com>
To: kvm@...r.kernel.org
Cc: linux-kernel@...r.kernel.org, Sean Christopherson <seanjc@...gle.com>,
Paolo Bonzini <pbonzini@...hat.com>, linux-kselftest@...r.kernel.org, Shuah
Khan <shuah@...nel.org>
Subject: Re: [PATCH] KVM: selftests: fix max_guest_memory_test with more
that 256 vCPUs
On Fri, 2024-03-15 at 10:35 -0400, Maxim Levitsky wrote:
> max_guest_memory_test uses ucalls to sync with the host, but
> it also resets the guest RIP back to its initial value in between
> tests stages.
>
> This makes the guest never reach the code which frees the ucall struct
> and since a fixed pool of 512 ucall structs is used, the test starts
> to fail when more that 256 vCPUs are used.
>
> Fix that by replacing the manual register reset with a loop in
> the guest code.
>
> Signed-off-by: Maxim Levitsky <mlevitsk@...hat.com>
> ---
> .../testing/selftests/kvm/max_guest_memory_test.c | 15 ++++++---------
> 1 file changed, 6 insertions(+), 9 deletions(-)
>
> diff --git a/tools/testing/selftests/kvm/max_guest_memory_test.c b/tools/testing/selftests/kvm/max_guest_memory_test.c
> index 6628dc4dda89f3c..1a6da7389bf1f5b 100644
> --- a/tools/testing/selftests/kvm/max_guest_memory_test.c
> +++ b/tools/testing/selftests/kvm/max_guest_memory_test.c
> @@ -22,10 +22,11 @@ static void guest_code(uint64_t start_gpa, uint64_t end_gpa, uint64_t stride)
> {
> uint64_t gpa;
>
> - for (gpa = start_gpa; gpa < end_gpa; gpa += stride)
> - *((volatile uint64_t *)gpa) = gpa;
> -
> - GUEST_DONE();
> + for (;;) {
> + for (gpa = start_gpa; gpa < end_gpa; gpa += stride)
> + *((volatile uint64_t *)gpa) = gpa;
> + GUEST_SYNC(0);
> + }
> }
>
> struct vcpu_info {
> @@ -55,7 +56,7 @@ static void rendezvous_with_boss(void)
> static void run_vcpu(struct kvm_vcpu *vcpu)
> {
> vcpu_run(vcpu);
> - TEST_ASSERT_EQ(get_ucall(vcpu, NULL), UCALL_DONE);
> + TEST_ASSERT_EQ(get_ucall(vcpu, NULL), UCALL_SYNC);
> }
>
> static void *vcpu_worker(void *data)
> @@ -64,17 +65,13 @@ static void *vcpu_worker(void *data)
> struct kvm_vcpu *vcpu = info->vcpu;
> struct kvm_vm *vm = vcpu->vm;
> struct kvm_sregs sregs;
> - struct kvm_regs regs;
>
> vcpu_args_set(vcpu, 3, info->start_gpa, info->end_gpa, vm->page_size);
>
> - /* Snapshot regs before the first run. */
> - vcpu_regs_get(vcpu, ®s);
> rendezvous_with_boss();
>
> run_vcpu(vcpu);
> rendezvous_with_boss();
> - vcpu_regs_set(vcpu, ®s);
> vcpu_sregs_get(vcpu, &sregs);
> #ifdef __x86_64__
> /* Toggle CR0.WP to trigger a MMU context reset. */
Kind ping on this patch.
Best regards,
Maxim Levitsky
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