Re: [PATCH kernel 3/3] powerpc/pseries/iommu: Do not use H_PUT_TCE_INDIRECT in secure VM
From: Michael Ellerman <mpe@ellerman.id.au>
Date: 2019-12-13 10:22:35
Alexey Kardashevskiy [off-list ref] writes:
H_PUT_TCE_INDIRECT uses a 4K page with TCEs to allow handling up to 512 TCEs per hypercall. While it is a decent optimization, we rather share less of secure VM memory so let's avoid sharing. This only allows H_PUT_TCE_INDIRECT for normal (not secure) VMs. This keeps using H_STUFF_TCE as it does not require sharing. Signed-off-by: Alexey Kardashevskiy <redacted> --- Possible alternatives are: 1. define FW_FEATURE_STUFFTCE (to allow H_STUFF_TCE) in addition to FW_FEATURE_MULTITCE (make it only enable H_PUT_TCE_INDIRECT) and enable only FW_FEATURE_STUFFTCE for SVM; pro = no SVM mention in iommu.c, con = a FW feature bit with very limited use
Yes let's do that please. Actually let's rename FW_FEATURE_MULTITCE to FW_FEATURE_PUT_TCE_IND (?) to make it clear that's what it controls now. You should just be able to add two entries to hypertas_fw_features_table that both look for "hcall-multi-tce". And then the SVM code disables the PUT_TCE_IND feature at some point. cheers
quoted hunk ↗ jump to hunk
2. disable FW_FEATURE_MULTITCE and loose H_STUFF_TCE which adds a delay in booting process --- arch/powerpc/platforms/pseries/iommu.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-)diff --git a/arch/powerpc/platforms/pseries/iommu.c b/arch/powerpc/platforms/pseries/iommu.c index f6e9b87c82fc..2334a67c7614 100644 --- a/arch/powerpc/platforms/pseries/iommu.c +++ b/arch/powerpc/platforms/pseries/iommu.c@@ -192,7 +192,8 @@ static int tce_buildmulti_pSeriesLP(struct iommu_table *tbl, long tcenum, int ret = 0; unsigned long flags; - if ((npages == 1) || !firmware_has_feature(FW_FEATURE_MULTITCE)) { + if ((npages == 1) || !firmware_has_feature(FW_FEATURE_MULTITCE) || + is_secure_guest()) { return tce_build_pSeriesLP(tbl->it_index, tcenum, tbl->it_page_shift, npages, uaddr, direction, attrs);@@ -402,7 +403,8 @@ static int tce_setrange_multi_pSeriesLP(unsigned long start_pfn, u64 rc = 0; long l, limit; - if (!firmware_has_feature(FW_FEATURE_MULTITCE)) { + if (!firmware_has_feature(FW_FEATURE_MULTITCE) || + is_secure_guest()) { unsigned long tceshift = be32_to_cpu(maprange->tce_shift); unsigned long dmastart = (start_pfn << PAGE_SHIFT) + be64_to_cpu(maprange->dma_base);-- 2.17.1