linux-kernel - Re: [Patch v3 13/14] PCI: hv: Add hypercalls to read/write MMIO space

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Date:   Thu, 17 Nov 2022 15:16:38 +0000
From:   Wei Liu <wei.liu@...nel.org>
To:     Michael Kelley <mikelley@...rosoft.com>
Cc:     hpa@...or.com, kys@...rosoft.com, haiyangz@...rosoft.com,
        wei.liu@...nel.org, decui@...rosoft.com, luto@...nel.org,
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        linux-pci@...r.kernel.org, linux-arch@...r.kernel.org,
        iommu@...ts.linux.dev
Subject: Re: [Patch v3 13/14] PCI: hv: Add hypercalls to read/write MMIO space

On Wed, Nov 16, 2022 at 10:41:36AM -0800, Michael Kelley wrote:
[...]
>  
> +static void hv_pci_read_mmio(struct device *dev, phys_addr_t gpa, int size, u32 *val)
> +{
> +	struct hv_mmio_read_input *in;
> +	struct hv_mmio_read_output *out;
> +	u64 ret;
> +
> +	/*
> +	 * Must be called with interrupts disabled so it is safe
> +	 * to use the per-cpu input argument page.  Use it for
> +	 * both input and output.
> +	 */

Perhaps adding something along this line?

	WARN_ON(!irqs_disabled());

I can fold this in if you agree.

> +	in = *this_cpu_ptr(hyperv_pcpu_input_arg);
> +	out = *this_cpu_ptr(hyperv_pcpu_input_arg) + sizeof(*in);
> +	in->gpa = gpa;
> +	in->size = size;
> +
> +	ret = hv_do_hypercall(HVCALL_MMIO_READ, in, out);
> +	if (hv_result_success(ret)) {
> +		switch (size) {
> +		case 1:
> +			*val = *(u8 *)(out->data);
> +			break;
> +		case 2:
> +			*val = *(u16 *)(out->data);
> +			break;
> +		default:
> +			*val = *(u32 *)(out->data);
> +			break;
> +		}
> +	} else
> +		dev_err(dev, "MMIO read hypercall error %llx addr %llx size %d\n",
> +				ret, gpa, size);
> +}
> +
> +static void hv_pci_write_mmio(struct device *dev, phys_addr_t gpa, int size, u32 val)
> +{
> +	struct hv_mmio_write_input *in;
> +	u64 ret;
> +
> +	/*
> +	 * Must be called with interrupts disabled so it is safe
> +	 * to use the per-cpu input argument memory.
> +	 */

Ditto.

Thanks,
Wei.