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Subject: Re: [PATCH v9 20/22] RISC-V: KVM: Fix race-condition in
 kvm_riscv_vcpu_sync_interrupts()
To:     Anup Patel <Anup.Patel@wdc.com>,
        Palmer Dabbelt <palmer@sifive.com>,
        Paul Walmsley <paul.walmsley@sifive.com>,
        Radim K <rkrcmar@redhat.com>
Cc:     Daniel Lezcano <daniel.lezcano@linaro.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Alexander Graf <graf@amazon.com>,
        Atish Patra <Atish.Patra@wdc.com>,
        Alistair Francis <Alistair.Francis@wdc.com>,
        Damien Le Moal <Damien.LeMoal@wdc.com>,
        Christoph Hellwig <hch@infradead.org>,
        Anup Patel <anup@brainfault.org>,
        "kvm@vger.kernel.org" <kvm@vger.kernel.org>,
        "linux-riscv@lists.infradead.org" <linux-riscv@lists.infradead.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
References: <20191016160649.24622-1-anup.patel@wdc.com>
 <20191016160649.24622-21-anup.patel@wdc.com>
From:   Paolo Bonzini <pbonzini@redhat.com>
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Date:   Mon, 21 Oct 2019 19:27:11 +0200
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On 16/10/19 18:12, Anup Patel wrote:
> +	/* Read current VSIP and VSIE CSRs */
> +	vsip = csr_read(CSR_VSIP);
> +	csr->vsie = csr_read(CSR_VSIE);
> +
> +	/* Sync-up VSIP.SSIP bit changes does by Guest */
> +	if ((csr->vsip ^ vsip) & (1UL << IRQ_S_SOFT)) {
> +		if (!test_and_set_bit(IRQ_S_SOFT, &v->irqs_pending_mask)) {
> +			if (vsip & (1UL << IRQ_S_SOFT))
> +				set_bit(IRQ_S_SOFT, &v->irqs_pending);
> +			else
> +				clear_bit(IRQ_S_SOFT, &v->irqs_pending);
> +		}

Looks good, but I wonder if this could just be "csr->vsip =
csr_read(CSR_VSIP)", which will be fixed up by flush_interrupts on the
next entry.

Paolo