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KVM: s390: use READ_ONCE() to read fpc register value

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Use READ_ONCE() to read a vcpu's floating point register value from
the memory mapped area. This avoids that, depending on code
generation, a different value is tested for validity than the one that
is used, since user space can modify the area concurrently and the
compiler is free to generate code that reads the value multiple times.

Reviewed-by: Christian Borntraeger <borntraeger@linux.ibm.com>
Reviewed-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>
This commit is contained in:
Heiko Carstens 2023-11-30 18:56:01 +01:00 committed by Alexander Gordeev
parent b988b1bb00
commit 3b2e00f167
1 changed files with 1 additions and 1 deletions
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2
arch/s390/kvm/kvm-s390.c
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@ -4962,7 +4962,7 @@ static void sync_regs(struct kvm_vcpu *vcpu)
current->thread.fpu.regs = vcpu->run->s.regs.vrs;
else
current->thread.fpu.regs = vcpu->run->s.regs.fprs;
current->thread.fpu.fpc = vcpu->run->s.regs.fpc;
current->thread.fpu.fpc = READ_ONCE(vcpu->run->s.regs.fpc);
if (test_fp_ctl(current->thread.fpu.fpc))
/* User space provided an invalid FPC, let's clear it */
current->thread.fpu.fpc = 0;