Commit bea8d237 authored by Daniel Henrique Barboza's avatar Daniel Henrique Barboza Committed by Anup Patel
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RISC-V: KVM: avoid EBUSY when writing same ISA val 



kvm_riscv_vcpu_set_reg_config() will return -EBUSY if the ISA config reg
is being written after the VCPU ran at least once.

The same restriction isn't placed in kvm_riscv_vcpu_get_reg_config(), so
there's a chance that we'll -EBUSY out on an ISA config reg write even
if the userspace intended no changes to it.

We'll allow the same form of 'lazy writing' that registers such as
zicbom/zicboz_block_size supports: avoid erroring out if userspace made
no changes to the ISA config reg.

Signed-off-by: default avatarDaniel Henrique Barboza <dbarboza@ventanamicro.com>
Reviewed-by: default avatarAndrew Jones <ajones@ventanamicro.com>
Signed-off-by: default avatarAnup Patel <anup@brainfault.org>
parent d57304bb

arch/riscv/kvm/vcpu_onereg.c

+7 −0
Original line number Diff line number Diff line
@@ -190,6 +190,13 @@ static int kvm_riscv_vcpu_set_reg_config(struct kvm_vcpu *vcpu, 
		if (fls(reg_val) >= RISCV_ISA_EXT_BASE)

			return -EINVAL;



		/*

		 * Return early (i.e. do nothing) if reg_val is the same

		 * value retrievable via kvm_riscv_vcpu_get_reg_config().

		 */

		if (reg_val == (vcpu->arch.isa[0] & KVM_RISCV_BASE_ISA_MASK))

			break;



		if (!vcpu->arch.ran_atleast_once) {

			/* Ignore the enable/disable request for certain extensions */

			for (i = 0; i < RISCV_ISA_EXT_BASE; i++) {