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Message-ID: <fc5b7217-49b5-4ca0-b4f7-0eab5000a2e4@amd.com>
Date: Thu, 3 Oct 2024 23:15:53 +0700
From: "Suthikulpanit, Suravee" <suravee.suthikulpanit@....com>
To: Jason Gunthorpe <jgg@...dia.com>
Cc: linux-kernel@...r.kernel.org, iommu@...ts.linux.dev, joro@...tes.org,
robin.murphy@....com, vasant.hegde@....com, kevin.tian@...el.com,
jon.grimm@....com, santosh.shukla@....com, pandoh@...gle.com,
kumaranand@...gle.com
Subject: Re: [PATCH v4 2/6] iommu/amd: Introduce helper function to update
256-bit DTE
On 9/27/2024 2:46 AM, Jason Gunthorpe wrote:
> On Mon, Sep 16, 2024 at 05:18:01PM +0000, Suravee Suthikulpanit wrote:
>
> ....
>
>> + if (!(ptr->data[0] & DTE_FLAG_V)) {
>> + /* Existing DTE is not valid. */
>> + write_upper(ptr, new);
>> + write_lower(ptr, new);
>> + iommu_flush_sync_dte(iommu, dev_data->devid);
>> + } else if (!(new->data[0] & DTE_FLAG_V)) {
>> + /* Existing DTE is valid. New DTE is not valid. */
>> + write_lower(ptr, new);
>> + write_upper(ptr, new);
>> + iommu_flush_sync_dte(iommu, dev_data->devid);
>> + } else {
>> + /* Existing & new DTEs are valid. */
>> + if (!FIELD_GET(DTE_FLAG_GV, ptr->data[0])) {
>> + /* Existing DTE has no guest page table. */
>> + write_upper(ptr, new);
>> + write_lower(ptr, new);
>> + iommu_flush_sync_dte(iommu, dev_data->devid);
>> + } else if (!FIELD_GET(DTE_FLAG_GV, new->data[0])) {
>> + /*
>> + * Existing DTE has guest page table,
>> + * new DTE has no guest page table,
>> + */
>> + write_lower(ptr, new);
>> + write_upper(ptr, new);
>> + iommu_flush_sync_dte(iommu, dev_data->devid);
>> + } else {
>> + /*
>> + * Existing DTE has guest page table,
>> + * new DTE has guest page table.
>> + */
>> + struct dev_table_entry clear = {};
>> +
>> + /* First disable DTE */
>> + write_lower(ptr, &clear);
>> + iommu_flush_sync_dte(iommu, dev_data->devid);
>> +
>> + /* Then update DTE */
>> + write_upper(ptr, new);
>> + write_lower(ptr, new);
>> + iommu_flush_sync_dte(iommu, dev_data->devid);
>> + }
>
> There is one branch missing where GV is valid in both and the [1]
> doesn't change. Ie atomic replace of a GCR3 table.
Not sure if I follow this.
> And maybe this will need more branches later for the viommu stuff?
I will take care of this later once we introduce the change for vIOMMU
stuff.
> But otherwise yes this captures what is needed just fine.
>
> Reviewed-by: Jason Gunthorpe <jgg@...dia.com>
>
>> @@ -1256,6 +1342,16 @@ static int iommu_flush_dte(struct amd_iommu *iommu, u16 devid)
>> +int iommu_flush_sync_dte(struct amd_iommu *iommu, u16 devid)
>> +{
>> + int ret;
>> +
>> + ret = iommu_flush_dte(iommu, devid);
>> + if (!ret)
>> + iommu_completion_wait(iommu);
>> + return ret;
>> +}
>
> Maybe this doesn't need to return an error since we can't handle
> failure to flush DTE tables..
Okey.
Thanks,
Suravee
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