From c52af96fdcac9eff31465f39c0ffcceadca9ac9f Mon Sep 17 00:00:00 2001 From: Oleksandr Tyshchenko Date: Thu, 27 Jan 2022 21:55:51 +0200 Subject: [PATCH] iommu/ipmmu-vmsa: Use refcount for the micro-TLBs Reference-count the micro-TLBs as several bus masters can be connected to the same micro-TLB (and drop TODO comment). This wasn't an issue so far, since the platform devices (this driver deals with) get assigned/deassigned together during domain creation/destruction. But, in order to support PCI devices (which are hot-pluggable) in the near future we will need to take care of. Signed-off-by: Oleksandr Tyshchenko Reviewed-by: Yoshihiro Shimoda --- xen/drivers/passthrough/arm/ipmmu-vmsa.c | 21 +++++++++++++++------ 1 file changed, 15 insertions(+), 6 deletions(-) diff --git a/xen/drivers/passthrough/arm/ipmmu-vmsa.c b/xen/drivers/passthrough/arm/ipmmu-vmsa.c index 649b9f6362..c912120411 100644 --- a/xen/drivers/passthrough/arm/ipmmu-vmsa.c +++ b/xen/drivers/passthrough/arm/ipmmu-vmsa.c @@ -127,6 +127,7 @@ struct ipmmu_vmsa_device { spinlock_t lock; /* Protects ctx and domains[] */ DECLARE_BITMAP(ctx, IPMMU_CTX_MAX); struct ipmmu_vmsa_domain *domains[IPMMU_CTX_MAX]; + unsigned int utlb_refcount[IPMMU_UTLB_MAX]; const struct ipmmu_features *features; }; @@ -468,12 +469,17 @@ static int ipmmu_utlb_enable(struct ipmmu_vmsa_domain *domain, } /* - * TODO: Reference-count the micro-TLB as several bus masters can be - * connected to the same micro-TLB. + * Reference-count the micro-TLBs as several bus masters can be connected + * to the same micro-TLB. The platform devices get assigned/deassigned + * together during domain creation/destruction. The PCI devices which use + * the same micro-TLB must also be hot-(un)plugged together. */ - ipmmu_imuasid_write(mmu, utlb, 0); - ipmmu_imuctr_write(mmu, utlb, imuctr | - IMUCTR_TTSEL_MMU(domain->context_id) | IMUCTR_MMUEN); + if ( mmu->utlb_refcount[utlb]++ == 0 ) + { + ipmmu_imuasid_write(mmu, utlb, 0); + ipmmu_imuctr_write(mmu, utlb, imuctr | + IMUCTR_TTSEL_MMU(domain->context_id) | IMUCTR_MMUEN); + } return 0; } @@ -484,7 +490,10 @@ static void ipmmu_utlb_disable(struct ipmmu_vmsa_domain *domain, { struct ipmmu_vmsa_device *mmu = domain->mmu; - ipmmu_imuctr_write(mmu, utlb, 0); + ASSERT(mmu->utlb_refcount[utlb] > 0); + + if ( --mmu->utlb_refcount[utlb] == 0 ) + ipmmu_imuctr_write(mmu, utlb, 0); } /* Domain/Context Management */ -- 2.30.2