From 12dce7ea5a84e0f107710f8df1cfb2dfe306c793 Mon Sep 17 00:00:00 2001 From: Juergen Gross Date: Thu, 4 Jul 2019 16:02:52 +0200 Subject: [PATCH] x86: make loading of GDT at context switch more modular In preparation for core scheduling, carve out the GDT related functionality (writing GDT related PTEs, loading default of full GDT) into sub-functions. Signed-off-by: Juergen Gross Acked-by: Jan Beulich Acked-by: Andrew Cooper --- xen/arch/x86/domain.c | 57 ++++++++++++++++++++++++++----------------- 1 file changed, 35 insertions(+), 22 deletions(-) diff --git a/xen/arch/x86/domain.c b/xen/arch/x86/domain.c index 894d8673e2..84cafbe558 100644 --- a/xen/arch/x86/domain.c +++ b/xen/arch/x86/domain.c @@ -1640,6 +1640,37 @@ static inline bool need_full_gdt(const struct domain *d) return is_pv_domain(d) && !is_idle_domain(d); } +static void write_full_gdt_ptes(seg_desc_t *gdt, const struct vcpu *v) +{ + unsigned long mfn = virt_to_mfn(gdt); + l1_pgentry_t *pl1e = pv_gdt_ptes(v); + unsigned int i; + + for ( i = 0; i < NR_RESERVED_GDT_PAGES; i++ ) + l1e_write(pl1e + FIRST_RESERVED_GDT_PAGE + i, + l1e_from_pfn(mfn + i, __PAGE_HYPERVISOR_RW)); +} + +static void load_full_gdt(const struct vcpu *v, unsigned int cpu) +{ + struct desc_ptr gdt_desc = { + .limit = LAST_RESERVED_GDT_BYTE, + .base = GDT_VIRT_START(v), + }; + + lgdt(&gdt_desc); +} + +static void load_default_gdt(const seg_desc_t *gdt, unsigned int cpu) +{ + struct desc_ptr gdt_desc = { + .limit = LAST_RESERVED_GDT_BYTE, + .base = (unsigned long)(gdt - FIRST_RESERVED_GDT_ENTRY), + }; + + lgdt(&gdt_desc); +} + static void __context_switch(void) { struct cpu_user_regs *stack_regs = guest_cpu_user_regs(); @@ -1648,7 +1679,6 @@ static void __context_switch(void) struct vcpu *n = current; struct domain *pd = p->domain, *nd = n->domain; seg_desc_t *gdt; - struct desc_ptr gdt_desc; ASSERT(p != n); ASSERT(!vcpu_cpu_dirty(n)); @@ -1690,25 +1720,13 @@ static void __context_switch(void) gdt = !is_pv_32bit_domain(nd) ? per_cpu(gdt_table, cpu) : per_cpu(compat_gdt_table, cpu); - if ( need_full_gdt(nd) ) - { - unsigned long mfn = virt_to_mfn(gdt); - l1_pgentry_t *pl1e = pv_gdt_ptes(n); - unsigned int i; - for ( i = 0; i < NR_RESERVED_GDT_PAGES; i++ ) - l1e_write(pl1e + FIRST_RESERVED_GDT_PAGE + i, - l1e_from_pfn(mfn + i, __PAGE_HYPERVISOR_RW)); - } + if ( need_full_gdt(nd) ) + write_full_gdt_ptes(gdt, n); if ( need_full_gdt(pd) && ((p->vcpu_id != n->vcpu_id) || !need_full_gdt(nd)) ) - { - gdt_desc.limit = LAST_RESERVED_GDT_BYTE; - gdt_desc.base = (unsigned long)(gdt - FIRST_RESERVED_GDT_ENTRY); - - lgdt(&gdt_desc); - } + load_default_gdt(gdt, cpu); write_ptbase(n); @@ -1721,12 +1739,7 @@ static void __context_switch(void) if ( need_full_gdt(nd) && ((p->vcpu_id != n->vcpu_id) || !need_full_gdt(pd)) ) - { - gdt_desc.limit = LAST_RESERVED_GDT_BYTE; - gdt_desc.base = GDT_VIRT_START(n); - - lgdt(&gdt_desc); - } + load_full_gdt(n, cpu); if ( pd != nd ) cpumask_clear_cpu(cpu, pd->dirty_cpumask); -- 2.39.5