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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [PATCH v8 2/2] xen/vpci: header: filter PCI capabilities
On Tue, Nov 28, 2023 at 02:44:25PM -0500, Stewart Hildebrand wrote:
> Currently, Xen vPCI only supports virtualizing the MSI and MSI-X capabilities.
> Hide all other PCI capabilities (including extended capabilities) from domUs
> for
> now, even though there may be certain devices/drivers that depend on being
> able
> to discover certain capabilities.
>
> We parse the physical PCI capabilities linked list and add vPCI register
> handlers for the next elements, inserting our own next value, thus presenting
> a
> modified linked list to the domU.
>
> Introduce helper functions vpci_hw_read8 and vpci_read_val. The vpci_read_val
> helper function returns a fixed value, which may be used for RAZ registers, or
^ read as zero
> registers whose value doesn't change.
>
> Introduce pci_find_next_cap_ttl() helper while adapting the logic from
> pci_find_next_cap() to suit our needs, and implement the existing
> pci_find_next_cap() in terms of the new helper.
>
> Signed-off-by: Stewart Hildebrand <stewart.hildebrand@xxxxxxx>
LGTM, some nits below:
Reviewed-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
> ---
> v7->v8:
> * use to array instead of match function
> * include lib.h for ARRAY_SIZE
> * don't emulate PCI_CAPABILITY_LIST register if PCI_STATUS_CAP_LIST bit is not
> set in hardware
> * spell out RAZ/WI acronym
> * dropped R-b tag since the patch has changed moderately since the last rev
>
> v6->v7:
> * no change
>
> v5->v6:
> * add register handlers before status register handler in init_bars()
> * s/header->mask_cap_list/mask_cap_list/
>
> v4->v5:
> * use more appropriate types, continued
> * get rid of unnecessary hook function
> * add Jan's R-b
>
> v3->v4:
> * move mask_cap_list setting to this patch
> * leave pci_find_next_cap signature alone
> * use more appropriate types
>
> v2->v3:
> * get rid of > 0 in loop condition
> * implement pci_find_next_cap in terms of new pci_find_next_cap_ttl function
> so
> that hypothetical future callers wouldn't be required to pass &ttl.
> * change NULL to (void *)0 for RAZ value passed to vpci_read_val
> * change type of ttl to unsigned int
> * remember to mask off the low 2 bits of next in the initial loop iteration
> * change return type of pci_find_next_cap and pci_find_next_cap_ttl
> * avoid wrapping the PCI_STATUS_CAP_LIST condition by using ! instead of == 0
>
> v1->v2:
> * change type of ttl to int
> * use switch statement instead of if/else
> * adapt existing pci_find_next_cap helper instead of rolling our own
> * pass ttl as in/out
> * "pass through" the lower 2 bits of the next pointer
> * squash helper functions into this patch to avoid transient dead code
> situation
> * extended capabilities RAZ/WI
> ---
> xen/drivers/pci/pci.c | 31 ++++++++++++-------
> xen/drivers/vpci/header.c | 63 +++++++++++++++++++++++++++++++++++++++
> xen/drivers/vpci/vpci.c | 12 ++++++++
> xen/include/xen/pci.h | 3 ++
> xen/include/xen/vpci.h | 5 ++++
> 5 files changed, 104 insertions(+), 10 deletions(-)
>
> diff --git a/xen/drivers/pci/pci.c b/xen/drivers/pci/pci.c
> index 3569ccb24e9e..1645b3118220 100644
> --- a/xen/drivers/pci/pci.c
> +++ b/xen/drivers/pci/pci.c
> @@ -39,31 +39,42 @@ unsigned int pci_find_cap_offset(pci_sbdf_t sbdf,
> unsigned int cap)
> return 0;
> }
>
> -unsigned int pci_find_next_cap(pci_sbdf_t sbdf, unsigned int pos,
> - unsigned int cap)
> +unsigned int pci_find_next_cap_ttl(pci_sbdf_t sbdf, unsigned int pos,
> + unsigned int *cap, unsigned int n,
> + unsigned int *ttl)
> {
> - u8 id;
> - int ttl = 48;
> + unsigned int id, i;
Nit: those can be defined inside the while loop.
> - while ( ttl-- )
> + while ( (*ttl)-- )
> {
> pos = pci_conf_read8(sbdf, pos);
> if ( pos < 0x40 )
> break;
>
> - pos &= ~3;
> - id = pci_conf_read8(sbdf, pos + PCI_CAP_LIST_ID);
> + id = pci_conf_read8(sbdf, (pos & ~3) + PCI_CAP_LIST_ID);
>
> if ( id == 0xff )
> break;
> - if ( id == cap )
> - return pos;
> + for ( i = 0; i < n; i++ )
> + {
> + if ( id == cap[i] )
> + return pos;
> + }
>
> - pos += PCI_CAP_LIST_NEXT;
> + pos = (pos & ~3) + PCI_CAP_LIST_NEXT;
> }
> +
> return 0;
> }
>
> +unsigned int pci_find_next_cap(pci_sbdf_t sbdf, unsigned int pos,
> + unsigned int cap)
> +{
> + unsigned int ttl = 48;
> +
> + return pci_find_next_cap_ttl(sbdf, pos, &cap, 1, &ttl) & ~3;
> +}
> +
> /**
> * pci_find_ext_capability - Find an extended capability
> * @sbdf: PCI device to query
> diff --git a/xen/drivers/vpci/header.c b/xen/drivers/vpci/header.c
> index 351318121e48..d7dc0c82a6ba 100644
> --- a/xen/drivers/vpci/header.c
> +++ b/xen/drivers/vpci/header.c
> @@ -18,6 +18,7 @@
> */
>
> #include <xen/iocap.h>
> +#include <xen/lib.h>
> #include <xen/sched.h>
> #include <xen/softirq.h>
> #include <xen/vpci.h>
> @@ -545,6 +546,68 @@ static int cf_check init_bars(struct pci_dev *pdev)
Could you please rename to init_header now that we do much more than
dealing with the BARs?
> if ( rc )
> return rc;
>
> + if ( !is_hardware_domain(pdev->domain) )
> + {
> + if ( pci_conf_read16(pdev->sbdf, PCI_STATUS) & PCI_STATUS_CAP_LIST )
> + {
> + /* Only expose capabilities to the guest that vPCI can handle. */
> + unsigned int next, ttl = 48;
> + unsigned int supported_caps[] = {
const?
We likely need to find a way to do this programmatically, so that when
a new capability is supported we don't need to go and modify the list
here every time. We can sort that out at a later point however.
> + PCI_CAP_ID_MSI,
> + PCI_CAP_ID_MSIX,
> + };
> +
> + next = pci_find_next_cap_ttl(pdev->sbdf, PCI_CAPABILITY_LIST,
> + supported_caps,
> + ARRAY_SIZE(supported_caps), &ttl);
> +
> + rc = vpci_add_register(pdev->vpci, vpci_read_val, NULL,
> + PCI_CAPABILITY_LIST, 1,
> + (void *)(uintptr_t)next);
> + if ( rc )
> + return rc;
> +
> + next &= ~3;
> +
> + if ( !next )
> + /*
> + * If we don't have any supported capabilities to expose to
> the
> + * guest, mask the PCI_STATUS_CAP_LIST bit in the status
> + * register.
> + */
> + mask_cap_list = true;
> +
> + while ( next && ttl )
> + {
> + unsigned int pos = next;
> +
> + next = pci_find_next_cap_ttl(pdev->sbdf,
> + pos + PCI_CAP_LIST_NEXT,
> + supported_caps,
> + ARRAY_SIZE(supported_caps),
> &ttl);
> +
> + rc = vpci_add_register(pdev->vpci, vpci_hw_read8, NULL,
> + pos + PCI_CAP_LIST_ID, 1, NULL);
> + if ( rc )
> + return rc;
> +
> + rc = vpci_add_register(pdev->vpci, vpci_read_val, NULL,
> + pos + PCI_CAP_LIST_NEXT, 1,
> + (void *)(uintptr_t)next);
> + if ( rc )
> + return rc;
> +
> + next &= ~3;
> + }
> + }
> +
> + /* Extended capabilities read as zero, write ignore */
> + rc = vpci_add_register(pdev->vpci, vpci_read_val, NULL, 0x100, 4,
> + (void *)0);
> + if ( rc )
> + return rc;
> + }
> +
> /* Utilize rsvdp_mask to hide PCI_STATUS_CAP_LIST from the guest. */
> rc = vpci_add_register_mask(pdev->vpci, vpci_hw_read16, vpci_hw_write16,
> PCI_STATUS, 2, NULL,
> diff --git a/xen/drivers/vpci/vpci.c b/xen/drivers/vpci/vpci.c
> index 96187b70141b..99307e310bbb 100644
> --- a/xen/drivers/vpci/vpci.c
> +++ b/xen/drivers/vpci/vpci.c
> @@ -137,6 +137,18 @@ static void cf_check vpci_ignored_write(
> {
> }
>
> +uint32_t cf_check vpci_read_val(
> + const struct pci_dev *pdev, unsigned int reg, void *data)
> +{
> + return (uintptr_t)data;
> +}
> +
> +uint32_t cf_check vpci_hw_read8(
> + const struct pci_dev *pdev, unsigned int reg, void *data)
> +{
> + return pci_conf_read8(pdev->sbdf, reg);
> +}
> +
> uint32_t cf_check vpci_hw_read16(
> const struct pci_dev *pdev, unsigned int reg, void *data)
> {
> diff --git a/xen/include/xen/pci.h b/xen/include/xen/pci.h
> index 50d7dfb2a2fd..b2dcef01a1cf 100644
> --- a/xen/include/xen/pci.h
> +++ b/xen/include/xen/pci.h
> @@ -205,6 +205,9 @@ int pci_mmcfg_read(unsigned int seg, unsigned int bus,
> int pci_mmcfg_write(unsigned int seg, unsigned int bus,
> unsigned int devfn, int reg, int len, u32 value);
> unsigned int pci_find_cap_offset(pci_sbdf_t sbdf, unsigned int cap);
> +unsigned int pci_find_next_cap_ttl(pci_sbdf_t sbdf, unsigned int pos,
> + unsigned int *cap, unsigned int n,
> + unsigned int *ttl);
> unsigned int pci_find_next_cap(pci_sbdf_t sbdf, unsigned int pos,
> unsigned int cap);
> unsigned int pci_find_ext_capability(pci_sbdf_t sbdf, unsigned int cap);
> diff --git a/xen/include/xen/vpci.h b/xen/include/xen/vpci.h
> index 8e8e42372ec1..3c14a74d6255 100644
> --- a/xen/include/xen/vpci.h
> +++ b/xen/include/xen/vpci.h
> @@ -52,7 +52,12 @@ uint32_t vpci_read(pci_sbdf_t sbdf, unsigned int reg,
> unsigned int size);
> void vpci_write(pci_sbdf_t sbdf, unsigned int reg, unsigned int size,
> uint32_t data);
>
> +uint32_t cf_check vpci_read_val(
> + const struct pci_dev *pdev, unsigned int reg, void *data);
A small comment could be helpful: helper to return the value passed in the data
parameter.
Thanks, Roger.
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