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Re: [PATCH v6 09/18] target/ppc: Streamline calculation of RMA limit fro
From: |
Greg Kurz |
Subject: |
Re: [PATCH v6 09/18] target/ppc: Streamline calculation of RMA limit from LPCR[RMLS] |
Date: |
Tue, 25 Feb 2020 18:05:31 +0100 |
On Tue, 25 Feb 2020 10:37:15 +1100
David Gibson <address@hidden> wrote:
> Currently we use a big switch statement in ppc_hash64_update_rmls() to work
> out what the right RMA limit is based on the LPCR[RMLS] field. There's no
> formula for this - it's just an arbitrary mapping defined by the existing
> CPU implementations - but we can make it a bit more readable by using a
> lookup table rather than a switch. In addition we can use the MiB/GiB
> symbols to make it a bit clearer.
>
> While there we add a bit of clarity and rationale to the comment about
> what happens if the LPCR[RMLS] doesn't contain a valid value.
>
> Signed-off-by: David Gibson <address@hidden>
> Reviewed-by: Cédric Le Goater <address@hidden>
> ---
> target/ppc/mmu-hash64.c | 71 ++++++++++++++++++++---------------------
> 1 file changed, 35 insertions(+), 36 deletions(-)
>
> diff --git a/target/ppc/mmu-hash64.c b/target/ppc/mmu-hash64.c
> index 0ef330a614..4f082d775d 100644
> --- a/target/ppc/mmu-hash64.c
> +++ b/target/ppc/mmu-hash64.c
> @@ -18,6 +18,7 @@
> * License along with this library; if not, see
> <http://www.gnu.org/licenses/>.
> */
> #include "qemu/osdep.h"
> +#include "qemu/units.h"
> #include "cpu.h"
> #include "exec/exec-all.h"
> #include "exec/helper-proto.h"This tool was originally developed to fix
> Linux CPU throttling issues affecting Lenovo T480 / T480s / X1C6 as described
> here.
> @@ -757,6 +758,39 @@ static void ppc_hash64_set_c(PowerPCCPU *cpu, hwaddr
> ptex, uint64_t pte1)
> stb_phys(CPU(cpu)->as, base + offset, (pte1 & 0xff) | 0x80);
> }
>
> +static target_ulong rmls_limit(PowerPCCPU *cpu)
> +{
> + CPUPPCState *env = &cpu->env;
> + /*
> + * This is the full 4 bits encoding of POWER8. Previous
> + * CPUs only support a subset of these but the filtering
> + * is done when writing LPCR
> + */
> + const target_ulong rma_sizes[] = {
> + [0] = 0,
> + [1] = 16 * GiB,
> + [2] = 1 * GiB,
> + [3] = 64 * MiB,
> + [4] = 256 * MiB,
> + [5] = 0,
> + [6] = 0,
> + [7] = 128 * MiB,
> + [8] = 32 * MiB,
> + };
> + target_ulong rmls = (env->spr[SPR_LPCR] & LPCR_RMLS) >> LPCR_RMLS_SHIFT;
> +
> + if (rmls < ARRAY_SIZE(rma_sizes)) {
This condition is always true since the RMLS field is 4-bit long... I guess
you want to check that RMLS encodes a valid RMA size instead.
if (rma_sizes[rmls]) {
> + return rma_sizes[rmls];
> + } else {
> + /*
> + * Bad value, so the OS has shot itself in the foot. Return a
> + * 0-sized RMA which we expect to trigger an immediate DSI or
> + * ISI
> + */
> + return 0;
> + }
> +}
> +
> int ppc_hash64_handle_mmu_fault(PowerPCCPU *cpu, vaddr eaddr,
> int rwx, int mmu_idx)
> {
> @@ -1006,41 +1040,6 @@ void ppc_hash64_tlb_flush_hpte(PowerPCCPU *cpu,
> target_ulong ptex,
> cpu->env.tlb_need_flush = TLB_NEED_GLOBAL_FLUSH | TLB_NEED_LOCAL_FLUSH;
> }
>
> -static void ppc_hash64_update_rmls(PowerPCCPU *cpu)
> -{
> - CPUPPCState *env = &cpu->env;
> - uint64_t lpcr = env->spr[SPR_LPCR];
> -
> - /*
> - * This is the full 4 bits encoding of POWER8. Previous
> - * CPUs only support a subset of these but the filtering
> - * is done when writing LPCR
> - */
> - switch ((lpcr & LPCR_RMLS) >> LPCR_RMLS_SHIFT) {
> - case 0x8: /* 32MB */
> - env->rmls = 0x2000000ull;
> - break;
> - case 0x3: /* 64MB */
> - env->rmls = 0x4000000ull;
> - break;
> - case 0x7: /* 128MB */
> - env->rmls = 0x8000000ull;
> - break;
> - case 0x4: /* 256MB */
> - env->rmls = 0x10000000ull;
> - break;
> - case 0x2: /* 1GB */
> - env->rmls = 0x40000000ull;
> - break;
> - case 0x1: /* 16GB */
> - env->rmls = 0x400000000ull;
> - break;
> - default:
> - /* What to do here ??? */
> - env->rmls = 0;
> - }
> -}
> -
> static void ppc_hash64_update_vrma(PowerPCCPU *cpu)
> {
> CPUPPCState *env = &cpu->env;
> @@ -1099,7 +1098,7 @@ void ppc_store_lpcr(PowerPCCPU *cpu, target_ulong val)
> CPUPPCState *env = &cpu->env;
>
> env->spr[SPR_LPCR] = val & pcc->lpcr_mask;
> - ppc_hash64_update_rmls(cpu);
> + env->rmls = rmls_limit(cpu);
> ppc_hash64_update_vrma(cpu);
> }
>
- [PATCH v6 13/18] spapr: Don't use weird units for MIN_RMA_SLOF, (continued)
[PATCH v6 17/18] spapr: Clean up RMA size calculation, David Gibson, 2020/02/24
[PATCH v6 14/18] spapr,ppc: Simplify signature of kvmppc_rma_size(), David Gibson, 2020/02/24