[SRU][O:linux-azure][PATCH 1/1] Revert "UBUNTU: SAUCE: clocksource: hyper-v: Use InvariantTSC and enable TSC page for a TDX VM without paravisor"

[John Cabaj]

BugLink: https://bugs.launchpad.net/bugs/2104836

This reverts commit 8e5f337e87d07427d229736d7b9678aa2472e1e2.

Upstream 7f828d5fff7d: "clocksource: hyper-v: Use lapic timer
in a TDX VM without paravisor" has since been committed to Ubuntu
kernels 6.8 and newer, which removes the need for this SAUCE patch.

Signed-off-by: John Cabaj <john.cabaj at canonical.com>
---
 arch/x86/entry/vdso/vma.c          | 11 +++--------
 arch/x86/kernel/cpu/mshyperv.c     |  8 ++++++++
 drivers/clocksource/hyperv_timer.c | 16 ++--------------
 3 files changed, 13 insertions(+), 22 deletions(-)

diff --git a/arch/x86/entry/vdso/vma.c b/arch/x86/entry/vdso/vma.c
index fe831afea305..6d83ceb7f1ba 100644
--- a/arch/x86/entry/vdso/vma.c
+++ b/arch/x86/entry/vdso/vma.c
@@ -17,7 +17,6 @@
 #include <linux/time_namespace.h>
 
 #include <asm/pvclock.h>
-#include <asm/mshyperv.h>
 #include <asm/vgtod.h>
 #include <asm/proto.h>
 #include <asm/vdso.h>
@@ -190,13 +189,9 @@ static vm_fault_t vvar_fault(const struct vm_special_mapping *sm,
 		}
 	} else if (sym_offset == image->sym_hvclock_page) {
 		pfn = hv_get_tsc_pfn();
-		if (pfn && vclock_was_used(VDSO_CLOCKMODE_HVCLOCK)) {
-			if (ms_hyperv.paravisor_present)
-				return vmf_insert_pfn(vma, vmf->address, pfn);
-			else
-				return vmf_insert_pfn_prot(vma, vmf->address,
-					pfn, pgprot_decrypted(vma->vm_page_prot));
-		}
+
+		if (pfn && vclock_was_used(VDSO_CLOCKMODE_HVCLOCK))
+			return vmf_insert_pfn(vma, vmf->address, pfn);
 	} else if (sym_offset == image->sym_timens_page) {
 		struct page *timens_page = find_timens_vvar_page(vma);
 
diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
index 290dcae609c8..e8e25d6e64cd 100644
--- a/arch/x86/kernel/cpu/mshyperv.c
+++ b/arch/x86/kernel/cpu/mshyperv.c
@@ -507,6 +507,14 @@ static void __init ms_hyperv_init_platform(void)
 			ms_hyperv.hints &= ~HV_X64_APIC_ACCESS_RECOMMENDED;
 
 			if (!ms_hyperv.paravisor_present) {
+				/*
+				 * Mark the Hyper-V TSC page feature as disabled
+				 * in a TDX VM without paravisor so that the
+				 * Invariant TSC, which is a better clocksource
+				 * anyway, is used instead.
+				 */
+				ms_hyperv.features &= ~HV_MSR_REFERENCE_TSC_AVAILABLE;
+
 				/*
 				 * The Invariant TSC is expected to be available
 				 * in a TDX VM without paravisor, but if not,
diff --git a/drivers/clocksource/hyperv_timer.c b/drivers/clocksource/hyperv_timer.c
index 513f1510fc4a..b39dee7b93af 100644
--- a/drivers/clocksource/hyperv_timer.c
+++ b/drivers/clocksource/hyperv_timer.c
@@ -22,7 +22,6 @@
 #include <linux/irq.h>
 #include <linux/acpi.h>
 #include <linux/hyperv.h>
-#include <linux/set_memory.h>
 #include <clocksource/hyperv_timer.h>
 #include <asm/hyperv-tlfs.h>
 #include <asm/mshyperv.h>
@@ -405,8 +404,8 @@ static __always_inline u64 read_hv_clock_msr(void)
 
 static union {
 	struct ms_hyperv_tsc_page page;
-	u8 reserved[SZ_2M];
-} tsc_pg __bss_decrypted __aligned(SZ_2M);
+	u8 reserved[PAGE_SIZE];
+} tsc_pg __bss_decrypted __aligned(PAGE_SIZE);
 
 static struct ms_hyperv_tsc_page *tsc_page = &tsc_pg.page;
 static unsigned long tsc_pfn;
@@ -547,7 +546,6 @@ static __always_inline void hv_setup_sched_clock(void *sched_clock) {}
 static void __init hv_init_tsc_clocksource(void)
 {
 	union hv_reference_tsc_msr tsc_msr;
-	int ret;
 
 	/*
 	 * If Hyper-V offers TSC_INVARIANT, then the virtualized TSC correctly
@@ -567,12 +565,6 @@ static void __init hv_init_tsc_clocksource(void)
 
 	hv_read_reference_counter = read_hv_clock_tsc;
 
-	if (hv_isolation_type_tdx() && !ms_hyperv.paravisor_present) {
-		ret = set_memory_decrypted((unsigned long)tsc_page, SZ_2M/PAGE_SIZE);
-		BUG_ON(ret);
-		memset(tsc_page, 0, PAGE_SIZE);
-	}
-
 	/*
 	 * TSC page mapping works differently in root compared to guest.
 	 * - In guest partition the guest PFN has to be passed to the
@@ -596,10 +588,6 @@ static void __init hv_init_tsc_clocksource(void)
 		tsc_pfn = HVPFN_DOWN(virt_to_phys(tsc_page));
 	tsc_msr.enable = 1;
 	tsc_msr.pfn = tsc_pfn;
-
-	if (hv_isolation_type_tdx() && !ms_hyperv.paravisor_present)
-		tsc_msr.pfn = PHYS_PFN(cc_mkdec(PFN_PHYS(tsc_msr.pfn)));
-
 	hv_set_msr(HV_MSR_REFERENCE_TSC, tsc_msr.as_uint64);
 
 	clocksource_register_hz(&hyperv_cs_tsc, NSEC_PER_SEC/100);
-- 
2.43.0