Messages in this thread | | | Subject | Re: [RFC v1 1/2] powerpc/pseries/iommu: Share the per-cpu TCE page with the hypervisor. | From | Alexey Kardashevskiy <> | Date | Thu, 7 Nov 2019 16:58:55 +1100 |
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On 07/11/2019 04:01, Ram Pai wrote: > On Wed, Nov 06, 2019 at 12:58:50PM +1100, Alexey Kardashevskiy wrote: >> >> >> On 05/11/2019 08:28, Ram Pai wrote: >>> The hypervisor needs to access the contents of the page holding the TCE >>> entries while setting up the TCE entries in the IOMMU's TCE table. For >>> SecureVMs, since this page is encrypted, the hypervisor cannot access >>> valid entries. Share the page with the hypervisor. This ensures that the >>> hypervisor sees the valid entries. >>> >>> Signed-off-by: Ram Pai <linuxram@us.ibm.com> >>> --- >>> arch/powerpc/platforms/pseries/iommu.c | 20 +++++++++++++++++--- >>> 1 file changed, 17 insertions(+), 3 deletions(-) >>> >>> diff --git a/arch/powerpc/platforms/pseries/iommu.c b/arch/powerpc/platforms/pseries/iommu.c >>> index 8d9c2b1..07f0847 100644 >>> --- a/arch/powerpc/platforms/pseries/iommu.c >>> +++ b/arch/powerpc/platforms/pseries/iommu.c >>> @@ -37,6 +37,7 @@ >>> #include <asm/mmzone.h> >>> #include <asm/plpar_wrappers.h> >>> #include <asm/svm.h> >>> +#include <asm/ultravisor.h> >>> >>> #include "pseries.h" >>> >>> @@ -179,6 +180,19 @@ static int tce_build_pSeriesLP(struct iommu_table *tbl, long tcenum, >>> >>> static DEFINE_PER_CPU(__be64 *, tce_page); >>> >>> +/* >>> + * Allocate a tce page. If secure VM, share the page with the hypervisor. >>> + */ >>> +static __be64 *alloc_tce_page(void) >>> +{ >>> + __be64 *tcep = (__be64 *)__get_free_page(GFP_ATOMIC); >>> + >>> + if (tcep && is_secure_guest()) >>> + uv_share_page(PHYS_PFN(__pa(tcep)), 1); >> >> >> There is no matching unshare in this patch. > > The page is allocated and shared, and stays that way for the life of the > kernel. It is not explicitly unshared or freed.
Ah, fair enough, I missed that, strange that we do not free it but ok. Thanks,
> It is however > implicitly unshared by the guest kernel, through a UV_UNSHARE_ALL_PAGES ucall > when the guest kernel reboots. And it also gets implicitly unshared by > the Ultravisor/Hypervisor, if the SVM abruptly terminates. > >> >> >>> + >>> + return tcep; >>> +} >>> + >>> static int tce_buildmulti_pSeriesLP(struct iommu_table *tbl, long tcenum, >>> long npages, unsigned long uaddr, >>> enum dma_data_direction direction, >>> @@ -206,8 +220,7 @@ static int tce_buildmulti_pSeriesLP(struct iommu_table *tbl, long tcenum, >>> * from iommu_alloc{,_sg}() >>> */ >>> if (!tcep) { >>> - tcep = (__be64 *)__get_free_page(GFP_ATOMIC); >>> - /* If allocation fails, fall back to the loop implementation */ >>> + tcep = alloc_tce_page(); >>> if (!tcep) { >>> local_irq_restore(flags); >>> return tce_build_pSeriesLP(tbl, tcenum, npages, uaddr, >>> @@ -391,6 +404,7 @@ static int tce_clearrange_multi_pSeriesLP(unsigned long start_pfn, >>> return rc; >>> } >>> >>> + >> >> Unrelated. > > yes. will fix it. > > Thanks, > RP >
-- Alexey
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